It has been a generalized method of diagnosis and treatment in medical practice to, with various equipments, measure electrical signals from a living body such as performing an electrocardiogram, electromyogram or electroencephalogram, and apply electric current (electrostimulation) to control functions of a living body. Such method uses an electrode, which is a part of the equipment, as an interface between the equipment and the living body.
The electrode used in the medical field generally includes electrically conducting wiring e.g. metal or carbon, and non-electrically conducting substrate material (e.g. plastic or glass). The electrode to be directly contact with a living body requires biocompatibility, and equipments being used nowadays still leave much to be improved in this respect.
Recently, researchers have noticed the merit of using a hydrogel, which is excellent in biocompatibility, in the substrate, and have started to develop techniques of adhering a hydrogel to an electrode material.
A known example of the adhesive technique is to place a hydrogel on an electrode material and perform electrolytic polymerization of conductive polymer to make the conductive polymers extend from the surface of the electrode material to the vicinity of the electrode material, thereby forming a conductive adhesive layer (see WO 2014/157550 (PTL 1) and M. Sasaki, et al., Advanced Healthcare Materials, 2014, 3, 1919. (NPL 1)). These documents report that polymer chains constituting the hydrogel intertwine with the conductive polymers, and in this way the electrode material and the hydrogel are firmly adhered together.